The present invention relates to containers formed from blanks of sheet material, e.g., corrugated fiberboard. More specifically, the invention concerns bulk boxes instantly manually erectable by the end user from a flat stackable box precursor, and blanks therefor. One use of such containers is for shipping and storing on pallets bulk quantities of dry flowable material (e.g., 1000-2000 lb. quantities of plastic beads or pellets used for injection molding).
Bulk boxes of the aforementioned variety are known. An exemplary construction is disclosed in U.S. Pat. Nos. 5,531,374 and 5,613,694 to Gasper. The Gasper boxes are erectable into an octagonal shape from a flat box precursor comprising opposed wall and floor forming panels. Manual pressure exerted inwardly on opposite folded vertical edges of the box precursor causes the opposing wall panels to separate from each other and form an octagonal shape tubular structure. At the same time, floor forming flaps previously lying flat against each other rotate, unfold and fold-over to form a box floor structure. A "band" structure is unfolded along a longitudinal fold line thereof to form, with a connecting member, a central floor region. Outer and central flaps provide floor surfaces flanking the band at the opposite box ends. Specifically, outer flap pairs at the opposite box ends are rotated and folded over to partially overlap the band on its bottom side. Central bottom flaps are positioned between the outer flaps at each end and are hingedly connected to the outer flaps by connecting web panels. Initially folded upon themselves, these flaps open up then fold over to partially overlap the band on its top side (inside the box).
In a variation of the design described in the Gasper patents, Creative Tech Marketing (assignee of the Gasper patents) has offered for sale a box wherein the outer bottom flaps are hingedly attached to the band and the central bottom flaps arm free from attachment to the outer bottom flaps. The outer bottom flaps rotate into a position underlying the band upon separation of the wall panels. It is then necessary to fold-over the central bottom flaps to a position underlying the outer bottom flap pairs.
In the typical bulk box application, the box floor serves merely to provide a protective layer between the box contents, e.g., dry flowable material, and a pallet support surface. Since the box floor obtains its structure strength from an underlying pallet, and the box is not intended to be lifted, when loaded, independently of a pallet, it is unnecessary for the floor structure to have substantial structural strength. On the other hand, the sidewalls of the bulk box must have considerable strength to resist the large outward bulge bulge forces generated by a flawable load, particularly in a lower part of the box, and to provide a stacking strength enabling multiple loaded containers (and underlying pallets) to be stacked upon each other. Regarding the latter, the sidewalls of bull boxes of the type described typically are configured to be able to withstand 10,000-18,000 lbs. in top-to-bottom compression.
In the Gasper designs, all the floor structure except a relatively small connecting member attaching separate panels of the band are formed integrally as an extension of the blank material to form the sidewall panels. Thus, the floor layer is composed largely of the same relatively high strength and high cost corrugation as is used for the sidewalls, when a much lower strength and lower cost grade of corrugation would serve just as well.
Another octagonal bulk box designed for quick set-up by the end user has been offered by Inland Paperboard and Packing Inc. of Indianapolis, Ind., as the "Quickset II." This construction is largely like the second Gasper design mentioned above, but with the corresponding band and connected outer bottom flaps being integrally formed as part of a floor blank separate from the main blank used to form the container sidewalls. The floor blank includes glue tabs for attachment of that blank about the inside lower edge of the main blank. As a separate piece, the floor blank can be made from a lighter grade of corrugation. However, the design still requires that the central bottom flaps be formed as integral extensions of the main blank used to form the wall panels, so that these flaps are constructed of higher strength and higher cost material than is necessary. Moreover, production of the two protruding central flaps requires die cutting of the blank from a rectangular piece of corrugation material having an overall extra width to provide for material to form the central flaps. This results in a high cost of material and to manufacture, and a substantial amount of unusable heavy scrap material for each blank which is produced.